Area array connector

ABSTRACT

Disclosed is an area array connector adapted to connect contact pads on one generally planar circuit element to corresponding contact pads on another generally planar circuit element. The connector has an insulative contact mounting sheet having a plurality of contact mounting apertures therein. A plurality of electrically conducting contacts are mounted in the contact mounting apertures, each contact having contact pad engaging legs resiliently projecting away from opposite faces of the contact mounting sheet. Two insulative contact securing sheets are provided, one laminated to each face of the contact mounting sheet, each contact securing sheet having apertures therein to accommodate the resiliently projecting legs of the contacts.

This invention relates to area array connectors which are adapted toconnect the contact pads on one generally planar circuit element, suchas a printed wiring board, to corresponding contact pads on anothergenerally planar circuit element.

SUMMARY OF THE INVENTION

In many electronic applications, compactness of the equipment, bothoverall and in detail, is an important goal. One manner of achievingthis is to stack printed wiring boards, or printed circuit boards, oneupon another, and electrically connecting them together face-to-faceinstead of in a more space consuming arrangement of daughter printedcircuit boards being connected together through current paths routedthrough a motherboard.

In order to make use of such a compact arrangement, it is necessary thatthe face-to-face connection be assuredly made both electrically andmechanically, and area array connectors are needed to connectcorresponding contact pads on adjacent printed circuit boards.

BACKGROUND OF THE INVENTION

In accordance with the invention, an area array connector is providedwhich is made up of the required number of electrically conductiveconnector elements or contacts carried in a three-layer laminatedinsulative housing. The contacts project from either side of the housingand are positioned to engage contact pads on printed circuit boards in astack, the connector being interleaved between adjacent printed circuitboards.

More specifically, in accordance with the invention, there is providedan area array connector adapted to connect the contact pads on onegenerally planar circuit element, such as a printed wiring board, to thecorresponding contact pads on another generally planar circuit elementor printed circuit board. The connector includes an insulative contactmounting sheet having a plurality of contact mounting apertures in it. Aplurality of electrically conducting contacts are mounted in the contactmounting apertures; each contact has contact pad engaging legsresiliently projecting away from opposite faces of the contact mountingsheet. Two insulative contact securing sheets are provided; onelaminated to each face of the contact mounting sheet. Each contactsecuring sheet has apertures in it to accommodate the resilientlyprojecting legs of said contacts.

In a preferred embodiment of the invention, each of the electricallyconducting contacts has a base leg adapted and proportioned to fit inand engage the contact mounting apertures of the contact mounting sheetand two pad engaging legs which are cantilevered resiliently outwardlyfrom the base leg in opposite directions. In accordance with onepreferred embodiment, it is preferred that the pad engaging legs of thecontacts have a shorter linear extent than the base legs of thecontacts. In such embodiment, in order to assure that the contacts aresecurely held in position, it is preferred that the contact mountingapertures are each greater in linear extent than the correspondingapertures of the contact securing sheets. In accordance with anotherembodiment, it is preferred that the pad engaging legs of the contactshave substantially the same length as the base legs of the contacts. Inthis embodiment, it is preferred that the thickness or width of at leastpart of the base legs be greater than the thickness or width of the padengaging legs. It is further preferred in all embodiments that thecontact mounting apertures are each greater in area than thecorresponding apertures in the contact securing sheets.

In accordance with the invention, it is preferred that the contacts arealigned with one another in a staggered pattern, or alternately that thecontacts are aligned with one another in a rectangular array, in whichthe spacing between adjacent contact projecting leg ends is less thanthe length of a projecting contact leg, and further in which thecontacts are skewed with respect to the alignment of the rectangulararray to accommodate the length of the projecting contact leg.

In accordance with another aspect of the invention, an assembly of aplurality of generally planar circuit elements is provided. The circuitelements have contact pads on at least one surface thereof, and arestacked one upon another, with area array connectors being interleavedbetween adjacent circuit elements. The area array connectors are made upof an insulative contact mounting sheet which has a plurality of contactmounting apertures therein, a plurality of electrically conductingcontacts mounted in the contact mounting apertures, each contact havingcontact pad engaging legs resiliently projecting away from oppositefaces of the contact mounting sheet, and two insulative contact securingsheets, one laminated to each face of the contact mounting sheet. Eachcontact securing sheet has apertures therein to accommodate theresiliently projecting legs of the contacts. Framing means are providedfor holding the assembly together and for establishing pressure contactbetween the contact pads and corresponding contact pad engaging legs. Itis preferred to have spacer means mounted in the sheets to establish andmaintain a uniform thickness of the connector.

In accordance with still another aspect of the invention, there isprovided a method for making an area array connector adapted to connectcontact pads on one generally planar circuit element to correspondingcontact pads on another generally planar circuit element that includesproviding an insulative generally planar contact mounting sheet,selecting positions on the contact mounting sheet at which contacts aredesired to be mounted, and laser machining contact-accommodatingapertures in the contact mounting sheet at said selected positionsthereon. Contacts of conducting material are formed, each contact havinga mounting leg for fitting into and engaging the contact-accommodatingapertures, and further having contact pad engaging legs resilientlyprojecting away from opposite faces of the contact mounting sheets. Thecontacts are mounted in the contact-accommodating apertures. Twoinsulative contact securing sheets are provided having apertures lasermachined therein which are registerable with the projecting legs ofcontacts mounted in the contact mounting sheet. One of the aperturedcontact securing sheets is adhesively laminated to each face of thecontact mounting sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the area array connector of theinvention;

FIG. 2 is an enlarged perspective view of a corner of the area arrayconnector of FIG. 1;

FIG. 3 is a still further enlarged view of a portion of the connector ofFIG. 1;

FIG. 4 is a perspective view of an assembly of printed circuit boardsand area array connectors of the invention;

FIG. 5 is an exploded view of the assembly of FIG. 4;

FIG. 6 is a cross-sectional view, partly in elevation, of one embodimentof the connector of the invention showing in enlarged scale a contactmounted in the insulative housing formed of three insulative sheets;

FIG. 7 is a cross-sectional view, partly in elevation, similar to FIG.6, of another embodiment of the invention on the same scale as FIG. 6;

FIG. 8 is a perspective view of a single contact of the invention;

FIG. 9 is an exploded view in perspective of the connector of FIG. 1;

FIG. 10 is an enlarged view of a portion of the contact mounting sheetforming the middle layer of the laminated connector of FIG. 9;

FIG. 11 is a perspective view of a connector showing the contacts inrectangular array, but with the individual contacts skewed in accordancewith the invention;

FIG. 12 is a perspective view of a connector showing the contactsarranged in staggered or triangular array; and

FIG. 13 is another perspective view of a single contact of the inventiondrawn to the same scale as FIGS. 11 and 12.

DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1 there is shown a connector of the invention designatedgenerally as 10. It is made up of three generally planar sheets, thecenter sheet being a contact mounting sheet 1, and the contact securingsheets 12 and 13 laminated to the sheet 11 on either face thereof. Anarray of contacts 14 is arranged on the connector as is indicated verydiagrammatically in FIG. 1, but which is shown on a larger scale insucceeding figures. The sheets 11, 12 and 13 are all made of insulativematerials, such as plastics (for example, phenolic, Teflon or Duroid(polytetrafluoroethylenes), diallyl phthalate (DAP)) or ceramics (forexample, aluminum oxide or beryllium oxide), and the sheets need not beall formed of the same material.

The laminated sheets 11, 12 and 13 are adhesively secured to one anotherby a suitable adhesive, such as epoxy or acrylic adhesives.

Attention is now directed to FIGS. 2 and 3, which show on differentscales contacts protruding through apertures in contact securing sheet13. The contacts are designated 14, and it can be seen that they aremade up of a contact leg 16, which projects into the aperture 15, andintegral with it a contact head 17, which also projects through theaperture 15. The contact head 17 is at the cantilevered end of thecontact leg 16, as will appear in greater detail below.

The laminated connector 10 has holes 18 in it positioned to pass framingbolts or studs (not shown) for building up an assembly of printedcircuit boards and array connectors and for aligning of the area arrayconnectors with the printed circuit boards that are interleaved withthem.

FIGS. 4 and 5 show an assembly designated generally 20. It is formed ofprinted circuit boards designated as 21 a, 21 b and 21 c. The circuitboards are of the kind having electric contact pads on at least onesurface thereof. Interleaved between the printed circuit boards are areaarray connectors 10. The assembly is held together by means of framingmembers 22 a and 22 b. Bolts or other fastening means (not shown) passthrough holes 18 in the framing members, the printed circuit boards, andthe area array connectors.

The parts of the assembly of FIG. 4 just discussed are shown in explodedform in FIG. 5 with the same reference characters being used. Thebefore-mentioned contact pads on the printed circuit boards aredesignated 23 in FIG. 5. The contacts 14 on the connectors 10 arepositioned to align with the contact pads 23.

FIG. 6 is a sectional view partly in elevation transversely through theconnector 10 at the location of a contact 14. From this figure, it canbe seen that the contact mounting sheet 11 has a slot 24 in it, which isgenerally aligned with slots or apertures 15, but which is longer orgreater in linear dimension than the apertures 15 in the contactsecuring sheets 13 and 12. FIG. 6 also shows that the contact 14 isgenerally E-shaped, having a base leg 25 centrally located in theE-shape. Base leg 25 terminates in an enlarged aperture engaging portion26 integrally formed therewith. The contact 14 has two contact padengaging legs 16 resiliently cantilevered or projecting away from thebase leg. The contact pad engaging legs 16 terminate in contacting heads17. The legs and heads taken together are proportioned so that thecontact legs resiliently project outwardly from the contact securingsheets, as well as the contact mounting sheet, yet can be resilientlymoved back into the laminate upon engaging a contact pad on an adjacentprinted circuit board with the contacting head almost flush with thesurface of the contact securing sheet.

FIG. 7 is similar to FIG. 6, but illustrates another preferredembodiment of the connector of the invention. Corresponding parts inthese two figures are given the same reference characters. In FIG. 7,the slot 24 in contact mounting sheet 11 is substantially the samelength as apertures 15. Slot 24 is, however, wider than apertures 15,and the surfaces of contact securing sheets 12 and 13 thus capture theenlarged portion 26 of base leg 25.

FIG. 8 shows a contact drawn in isolation with its parts marked with thesame reference characters as those used in FIGS. 6 and 7. The contact 14may be formed of a material having good electrical conducting propertiesand good resiliency or spring properties, such as beryllium copper, andthe actual points of contact with the contact pads of a printed circuitboard may be plated with gold or other materials for establishing goodelectrical contact.

FIG. 9 shows the connector 10 of FIG. 1 in exploded form, with all butone of the contacts 14 installed, and with the apertures 24 and 15 inthe sheets shown. Also seen in FIG. 9 are spacer means 29 which fit intoholes 30 in the sheets to help establish a uniform thickness to thelaminate when it is formed. Spacer means 29 are preferably longer thanthe combined thickness of the three sheets so that they, and not thesheets, establish the spacing between circuit boards.

FIG. 10 shows a contact mounting sheet 11 having slots 24 in it.Contacts 14 are shown mounted in the slots or apertures in sheet 11. Itcan be seen that the legs 16 terminating in heads 17 project outwardlyfrom the face of the contact mounting sheet 11. It can also be seen thataperture 24 in sheet 11 is contoured in profile to accommodate theenlarged end portion 26 of leg 25.

FIG. 11 shows a portion of a connector 10 in which the contact heads 17of the several connectors 14 are arranged in a rectangular grid. Thespacing of the grid is such that it is smaller than the linear length ofa contact, and for this reason, in accordance with the invention, thecontacts are skewed with respect to the rectangular layout so that theydo not interfere with the tightly arranged rectangular array.

FIG. 12 shows an arrangement of contacts 14 which is preferred to thatof FIG. 11. In this arrangement, the contact heads 17 are in a staggeredor triangular pattern. This makes for ease of manufacture.

FIG. 13 shows a contact 14 drawn to the same scale as the contacts inFIGS. 11 and 12.

In accordance with the method aspect of the invention, it is preferredthat the apertured sheets 11, 12 and 13 not be molded, as isconventional, but rather that the sheets be cut from larger stock andthe apertures machined in them by numerically controlled laser orequivalent techniques. This is advantageous because the area arrayconnectors are most often needed in relatively small numbers for a givendesign, and conventional tooling would be excessively costly. Inaddition, this manufacturing method provides very great flexibility inthe choice of number, size, shape, and positioning of the apertures,thus facilitating custom design of small production lots.

What is claimed is:
 1. An area array connector adapted to connectcontact pads on one generally planar circuit element to correspondingcontact pads on another generally planar circuit element comprising: aninsulative contact mounting sheet having a plurality of contact mountingapertures therein; a plurality of electrically conducting contactsmounted in said contact mounting apertures, each contact having contactpad engaging legs resiliently projecting away from opposite faces ofsaid contact mounting sheet; two insulative contact securing sheets, onelaminated to each face of said contact mounting sheet, each contactsecuring sheet having apertures therein to accommodate the resilientlyprojecting legs of said contacts; in which each of said electricallyconducting contacts comprises a base leg adapted and proportioned to fitin and engage the contact mounting apertures of said contact mountingsheet and two pad engaging legs cantilevered resiliently outwardly fromsaid base leg in opposite directions; in which said pad engaging legs ofsaid contacts have a shorter linear extent than the base legs of saidcontacts; and in which said contact mounting apertures are each greaterin linear extent than the corresponding apertures of said contactsecuring sheets.
 2. A connector in accordance with claim 1 in which saidcontacts are aligned with one another in a staggered pattern.
 3. Aconnector in accordance with claim 1 in which said contacts are alignedwith one another in a rectangular array, in which the spacing betweenadjacent contact projecting leg ends is less than the length of aprojecting contact leg, and further in which said contacts are skewedwith respect to the alignment of said rectangular array to accommodatethe length of said projecting contact leg.
 4. An assembly of a pluralityof generally planar circuit elements having contact pads on at least onesurface thereof, said circuit elements being stacked one upon another,with area array connectors being interleaved between adjacent circuitelements, said area array connectors each comprising: an insulativecontact mounting sheet having a plurality of contact mounting aperturestherein; a plurality of electrically conducting contacts mounted in saidcontact mounting apertures, each contact having contact pad engaginglegs resiliently projecting away from opposite faces of said contactmounting sheet; two insulative contact securing sheets, one laminated toeach face of said contact mounting sheet, each contact securing sheethaving apertures therein to accommodate the resiliently projecting legsof said contacts; and framing means for holding said assembly togetherand for establishing pressure contact between said contact pads andcorresponding contact pad engaging legs; spacer means mounted in saidsheets to establish and maintain a uniform thickness of said connector;and said spacer means having a length greater than the combinedthickness of said sheets.
 5. An assembly in accordance with claim 4 inwhich said plurality of generally planar circuit elements comprisesthree or more of said elements.
 6. An assembly in accordance with claim5 and further comprising spacer means mounted in said sheets toestablish and maintain a uniform thickness of said connector.
 7. Anassembly in accordance with claim 6 in which said spacer means have alength greater than the combined thickness of said sheets.